The present invention relates generally to an apparatus for heating fluids and more particularly to a friction furnace for heating circulating fluid.
There have been many attempts to provide a suitable device for heating fluids of a general type within which fluid is frictionally heated under forced circulation. Examples of such devices are shown in U.S. Pat. Nos. 823,856; 1,682,102; 3,164,147; and 4,004,553. U.S. Pat. Nos. 1,682,102; 3,164,147; and 4,004,553 are typical of the prior art in that they utilize a rotating means to induce friction in a fluid contained within the device. For example, U.S. Pat. No. 1,682,102 heats air within a casing by rotation of a plurality of paddle wheels alternately disposed in close proximity to a plurality of stationary partitions. Rotation of the paddle wheels creates compressive friction and turbulance in the fluid (air) which is then translated into heat.
Alternatively, U.S. Pat. No. 3,164,147 teaches rotation of rigid discs adjacently disposed and in contact with stationary discs such that the relative motion of the discs causes frictional heating thereof. Oil is then circulated within the discs in order to absorb and transfer this heat for external use. Similarily, U.S. Pat. No. 4,004,553 teaches the use of a rotating disc disposed in a narrow interspace within a housing. Fluid circulating through the device is heated by the rotational turbulence created therewithin.
Common to these examples of prior art, however, is the necessity for not only rotational motive force applied to the device but also the application of force to displace the fluid through the device. Such displacive force is provided in U.S. Pat. No. 1,682,102 by internal impeller wheels driven by the rotating means whereas in U.S. Pat. Nos. 3,164,147 and 4,004,553, displacive force is provided by external means. Unfortunately, high speed rotating devices built to close tolerance, as dictated by the nature of the prior art, are inherently expensive in both manufacture and operation and necessary coupling of a fluid displacive means only further complicates this art. Consequently, there is a need for a friction furnace which eliminates the need for rotating elements, thus simplifying manufacture as well as reducing the cost of operation and maintenance of such devices.
Another problem inherent in the friction furnace art is an inability to readily adapt a particular device to increase or decrease its heating capability in order to meet the needs of each particular application. U.S. Pat. No. 3,164,147 is typical as such in that modification of the device necessitates replacement of the rotating means in order to achieve higher rotational speeds and/or insertion of additional internal rotating devices thus necessitating extensive modification and/or replacement of the original casing. U.S. Pat. No. 4,004,553, for example, teaches the use of a plurality of component modules installed in series to achieve higher fluid heating values but this art also necessitates extensive modifications not readily adapted to each particular application. Consequently, there is an additional need for a friction furnace which may be readily adapted for increased and/or decreased heating demands of each particular application.
U.S. Pat. No. 823,856 presents one solution to these problems of rotational complexity and adaptability. However, the corrugated plates used therein severely restrict the adaptability of that device since the number of plates is limited by their necessarily concentric design. Additionally, these plates require extensive and costly machining of minute perforations in order to achieve the desired heating effect upon transversing air.
An additional problem found to be common in the prior art utilizing a circulating liquid, is the operational necessity to maintain internal fluid pressures of 1200 psi or greater. Such pressures, unfortunately, greatly increase the cost of manufacture and operation of the systems.
As a result, there is a need for a friction furnace which eliminates the costly necessity for both rotating and circulating means; is inexpensive to manufacture and operate; is simple and relatively uncomplicated in design; can be readily adapted to meet the heating requirements of a particular application; and can effectively operate at design pressures less than 1200 psi.